Batteries are widely used to provide electrical energy to portable devices. Although batteries are available in a variety of conventional sizes, shapes, and ratings, many devices are intended for use with only specially designed battery packs. While battery packs are often more expensive than conventional batteries, the use of battery packs may be preferable for a number of reasons.
For example, a battery pack may include storage cells designed to satisfy the particular power requirements of a device with which the battery pack will be used. Battery packs can also be designed to be coupled to the device more quickly, easily, and effectively than conventional batteries. Further, along with the storage cells, a battery pack may house additional components useful to the device and unavailable with standard batteries. Finally, the battery pack housing may provide better mechanical and environmental protection for the storage cells than is available with conventional batteries.
One application for battery packs that is of particular interest is the powering of medical instruments. As will be appreciated, a medical instrument may be used in emergency situations in which the instrument's power source must be absolutely dependable. However, as a battery pack is used, the energy stored by the battery pack is necessarily depleted and will eventually become inadequate to power the medical instrument. Unless the instrument is no longer needed or can be connected to an auxiliary source of power, the discharged battery pack must be removed and a charged battery pack inserted in its place. To minimize the resultant disruption in the instrument's operation, the battery pack employed must be quickly and easily replaceable.
One example of a medical instrument employing battery packs of the type described above is the LIFEPAK 5 portable defibrillator and ECG monitor sold by Physio-Control Corporation, the assignee of the present application. The defibrillator and ECG monitor can be interlocked or used independently and each is designed to be powered by a rechargeable battery pack.
In that regard, the battery packs are received within stowage recesses provided adjacent one comer of the defibrillator and one comer of the monitor. Each recess includes a floor, an end wall, and two sidewalls and is partially open at a connector end. A pair of male electrical connector posts are provided in the floor of the recess. The posts are located adjacent the connector end of the recess, spaced apart from the sidewalls.
The battery packs used with the defibrillator and monitor are interchangeable and have a substantially uniform rectangular cross section. Each battery pack has a top, a bottom, a beveled end, a connector end, and a pair of sidewalls. A pair of electrical receptacles are provided in the bottom of each battery pack, adjacent the connector end of the battery pack. The receptacles are designed to attach to the connector posts located in the recess.
Also provided at the connector end of the battery pack is a latch arm. The latch arm is molded as an integral part of the battery pack and extends upwardly from the bottom of the battery pack, midway between the two connectors. The free end of the latch arm is resiliently depressible toward the battery pack and includes a detent for engaging the recess, as will be described below.
A battery pack is connected to the defibrillator or monitor by first inserting the beveled end of the battery pack into the appropriate battery stowage recess. Then, the connector end of the battery pack is inserted into the connector end of the recess, causing the posts on the floor of the recess to electrically and mechanically engage the receptacles in the bottom of the battery pack. As this occurs, the free end of the latch arm on the battery pack is deflected by a lip included at the connector end of the receptacle. Given its resilient nature, the latch arm deflects until further insertion of the battery pack allows the detent on the free end of the latch arm to clear the lip, securely retaining the battery pack in the recess.
To remove the battery pack, the free end of the latch arm must be manually depressed to again allow the detent to clear the lip. Another lip located at the connector end of the battery pack then allows the battery pack to be lifted from the recess.
As will be appreciated, the particular battery pack described above is only one of a multitude of battery packs designed for various applications. Often, however, existing battery packs are not suitable for use with newly developed instruments and it is desirable to develop a new battery pack that can be quickly and easily attached to the instrument, that satisfies the power requirements of the instrument, and that does not disturb the general ergonomics of the instrument.